Polyalcoxyamines obtained from β-substituted nitroxides

ABSTRACT

The invention relates to polyalcoxyamines obtained from beta-substituted nitroxides of formula (1) wherein A represents a di- or polyvalent structure, R1 represents a molar mass of more than 15 and is a monovalent radical, and n&gt;2. The inventive compounds can be used as initiators for (co)polymerizations of at least one radically polymerizable monomer.

The present invention relates to polyalkoxyamines obtained fromβ-substituted nitroxides, which may be used especially as free-radicalpolymerization initiators.

Recent developments in controlled free-radical polymerization haverevealed the value of polyalkoxyamines as described in Accounts ofChemical Research, 1997, 30, pages 373-382.

These polyalkoxyamines, under the action of heat, in the presence of anolefin which may undergo free-radical polymerization, initiate thepolymerization while at the same time allowing it to be controlled.

The mechanism for this control may be represented diagrammatically asbelow:

with M representing a polymerizable olefin and P representing thegrowing polymer chain.

The key to the control is associated with the constants K_(deact),k_(act) and k_(p) (T. Fukuda and A. Goto, Macromolécules 1999, 32, pages618 to 623). If the ratio k_(deact)/k_(act) is too high, thepolymerization is blocked, whereas when the ratio k_(p)/k_(deact) is toohigh, when the ratio k_(deac)/k_(act) is too low though, thepolymerization is uncontrolled.

It has been found (P. Tordo et al., Polym. Prep. 1997, 38, pages 729 and730; and C. J. Hawker et al., Polym. mater. Sci. Eng., 1999, 80, pages90 and 91) that β-substituted alkoxyamines make it possible to initiateand control efficiently the polymerization of several types of monomers,whereas TEMPO-based alkoxyamines [such as(2′,2′,6′,6′-tetramethyl-1′-piperidyloxy-)methylbenzene mentioned inMacromolecules 1996, 29, pages 5245-5254] control only thepolymerizations of styrene derivatives.

The Applicant has now found that, starting with polyoxyamines of thegeneral formula (I):

in which n≧2,

A represents a polyfunctional core and R_(L) represents a radical with amolar mass of greater than 15, A and R_(L) will be defined more fullylater, it can synthesize polymers and copolymers with well definedarchitecture.

Starting with a dialkoxyamine of formula. (I) in which n=2, it ispossible to synthesize triblock copolymers, each block being derivedfrom monomers as different as alkyl acrylates and/or styrenederivatives, with excellent control of the polymerization and thepolydispersity and with very short polymerization reaction times.

Thus, for example, it is possible to polymerize successively 2 monomersM1 and M2:

By way of example, M1=alkyl acrylate and M2=styrene.

Starting from a trialkoxyamine, “star-shaped” polymers will be obtained.

One subject of the invention is thus polyalkoxyamines of general formula(I):

in which: n≧2,

A represents a divalent or polyvalent structure which may be chosen fromthe structures given below in a nonlimiting manner:

in which R¹ and R², which may be identical or different, represent alinear or branched alkyl radical containing a number of carbon atomsranging from 1 to 10, phenyl or thienyl radicals optionally substitutedwith a halogen atom such as F, Cl or Br, or a linear or branched alkylradical containing a number of carbon atoms ranging from 1 to 4, oralternatively with nitro, alkoxy, aryloxy, carbonyl or carboxylradicals; a benzyl radical, a cycloalkyl radical containing a number ofcarbon atoms ranging from 3 to 12, a radical comprising one or moreunsaturations; B represents a linear or branched alkylene radicalcontaining a number of carbon atoms ranging from 1 to 20; m is aninteger ranging from 1 to 10;

in which R³ and R⁴, which may be identical or different, represent aryl,pyridyl, furyl or thienyl radicals optionally substituted with a halogenatom such as F, Cl or Br, or with a linear or branched alkyl radicalcontaining a number of carbon atoms ranging from 1 to 4, oralternatively with nitro, alkoxy, aryloxy, carbonyl or carboxylradicals; D represents a linear or branched alkylene radical containinga number of carbon atoms ranging from 1 to 6, a phenylene radical or acycloalkylene radical; p ranging from 0 to 10;

in which R⁵, R⁶ and R⁷, which may be identical or different, have thesame meanings as R¹ and R² of formula (II), q, r and s are integersranging from 1 to 5;

in which R⁸ has the same meaning as R³ and R⁴ of formula (III), t is aninteger ranging from 1 to 4, u is ≧2 and ≦6;

in which R⁹ has the same meaning as the radical R⁸ of formula (V) and vis ≧2 and ≦6;

in which R¹⁰, R¹¹ and R¹², which may be identical or different,represent a phenyl radical, optionally substituted with a halogen atomsuch as Cl or Br, or with a linear or branched alkyl radical containinga number of carbon atoms ranging from 1 to 10; W represents an oxygen,sulfur or selenium atom, and w is equal to zero or 1;

in which R¹³ has the same meaning as R¹ of formula (II), and R¹⁴ has thesame meaning as R³ or R⁴ of formula (III);

in which R¹⁵ and R¹⁶, which may be identical or different, represent ahydrogen atom, a linear or branched alkyl radical containing a number ofcarbon atoms ranging from 1 to 10, or an aryl radical, optionallysubstituted with a halogen atom or a hetero atom,

R_(L) has a molar mass of greater than 15; the monovalent radical R_(L)is said to be in a β position relative to the nitrogen atom, theremaining valencies on the carbon atom and on the nitrogen atom informula (1) may be linked to various radicals such as a hydrogen atom, ahydrocarbon-based radical, for instance an alkyl, aryl or aralkylradical containing from 1 to 10 carbon atoms, the carbon atom and thenitrogen atom in formula (1) may also be linked together via a divalentradical so as to form a ring; preferably, however, the remainingvalencies on the carbon atom and on the nitrogen atom of formula (I) arelinked to monovalent radicals; preferably, the radical R_(L) has a molarmass of greater than 30, the radical R_(L) may have, for example, amolar mass of between 40 and 450; by way of example, the radical R_(L)may be a radical comprising a phosphoryl group, said radical R_(L)preferably being represented by the formula:

in which R¹⁷ and R¹⁸, which may be identical or different, may be chosenfrom alkyl, cycloalkyl, alkoxy, aryloxy, aryl, aralkyloxy,perfluoroalkyl and aralkyl radicals and may contain from 1 to 20 carbonatoms; R¹⁷ and/or R¹⁸ may also be a halogen atom, for instance achlorine or bromine or fluorine or iodine atom; the radical R_(L) mayalso comprise at least one aromatic ring such as the phenyl radical ornaphthyl radical, said radical possibly being substituted, for examplewith an alkyl radical containing from 1 to 10 carbon atoms.

According to the present invention, the monovalent radicals linked tothe carbon atom bearing the radical R_(L), which may be identical ordifferent, may be a hydrogen atom, a linear or branched alkyl radicalcontaining a number of carbon atoms ranging from 1 to 12, a phenylradical, or an aralkyl radical containing, for example, from 1 to 10carbon atoms. By way of illustration of such monovalent radicals,mention will be made of ethyl, butyl, tert-butyl and isopropyl radicals.

According to the present invention, the alkoxyamines of formula (I) inwhich n=2 and in which at least one of the remaining valencies on thecarbon atom bearing R_(L) is linked to a hydrogen atom, are mostparticularly preferred.

The two remaining valencies on the carbon atom may also be linked to adivalent radical so as to form a ring including the carbon atom bearingthe radical R_(L), said ring possibly containing a number of carbonatoms ranging from 3 to 10 and possibly containing a hetero atom such asN, O or S.

The remaining valency on the nitrogen atom may also be linked to a group—C(CH₃)₂Z with Z=—COOalkyl, —COOH, —CH₃, —CN, —CH₂OH, —CH₂OSi(CH₃)₃.

The polyalkoxyamines of formula (I) may be prepared according to methodsknown in the literature. The method most commonly used involves thecoupling of a carbon-based radical with a nitroxide radical. Thecoupling may be performed using a halo derivative A(X)_(n) in thepresence of an organometallic system, for instance CuX/ligand (X=Cl orBr) according to a reaction of ATRA (Atom Transfer Radical Addition)type as described by D. Greszta et al. in Macromolecules 1996, 29,7661-7670.

This method consists in transferring an atom or a group of atoms toanother molecule in the presence of an organometallic system CuX/ligandin a solvent medium, according to the scheme:

One procedure which is generally used consists in dissolving theorganometallic system such as CuBr/ligand in an organic solvent which ispreferably aromatic, such as benzene or toluene, and then in introducinginto the solution the compound A(X)_(n) and the β-substituted nitroxide

As examples of ligands used, mention will be made of bipyridine,4,4′-bis(5-nonyl)-2,2′-bipyridine and tris(2-pyridylmethyl)amine (TPA).

The reaction mixture is then stirred at a temperature between 20° C. and90° C. for a period which may be up to 48 hours, or even more.

Next, the precipitate is filtered off, rinsed with a solvent such asether and the filtrate is then washed with an aqueous solutioncontaining 5% by weight of CuSO₄ and then finally with water. Theresulting solution is dried over magnesium sulfate and the solvents arethen evaporated off under reduced pressure.

According to another particular advantageous procedure, a metal salt MXsuch as CuX, a ligand, the compound A(X)_(n) and the β-substitutednitroxide:

are mixed together with stirring in an organic solvent, in aβ-substituted nitroxide/A(X)_(n) molar ratio ranging from n to 2n, thereaction medium is kept stirring at a temperature of between 20° C. and90° C. until the β-substituted nitroxide has disappeared, the organicphase is recovered and washed with water, and the polyalkoxyamine (I) isthen isolated by evaporating off the organic solvent under reducedpressure.

As examples of ligands which may be used according to this procedure,mention will be made of:

tris[2-(dimethylamino)ethyl]amine:

N,N,N′,N′,N″-pentamethyldiethylenetriamine (PMDETA):

N,N,N′,N′-tetramethylethylenediamine:

(CH₃)₂—N—CH₂CH₂—N—CH₃)_(2′)

1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA):

cyclic polyamines such as:

1,4,7-trimethyl-1,4,7-triazacyclononane,

1,5,9-trimethyl-1,5,9-triazacyclododecane,

1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane.

PMDETA will preferably be used.

The oxidation state of the active species of metal M of the metal saltis equal to 1 (M^(I)).

This active species may be added as is to the reaction medium,preferably in the form of a metal halide such as CuBr.

The active species may also be generated in situ according to the redoxreaction:

M^(II)X+M⁰⇄2M^(I)X

using a metal salt M^(II)X such as CuBr₂ in which the metal M is inoxidation state 2 (M^(II)) and the same metal in oxidation state zero(M⁰).

A metal salt MX in which the metal M is in oxidation state 1 (M^(I)A)and the same metal M in oxidation state 0 (M⁰) may also be introducedinto the reaction medium.

According to this procedure, the ligand is used in a ligand/M^(I) molarratio ranging from 1 to 5 and preferably ranging from 1 to 2.

The β-substituted nitroxide/A(X)_(n) molar ratio ranges from n to 1.4nand preferably is in the region of 1.

As illustrations of β-substituted nitroxides

which may be used according to the present invention, mention will bemade of:

N-tert-butyl-1-phenyl-2-methylpropyl nitroxide,

N-(2-hydroxymethylpropyl)-1-phenyl-2-methylpropyl nitroxide),

N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide,

N-tert-butyl-1-dibenzylphosphono-2,2-dimethylpropyl nitroxide,

N-tert-butyl-1-bis(2,2,2-trifluoroethyl)phosphono-2,2-dimethylpropylnitroxide,

N-tert-butyl[(1-diethylphosphono)-2-methylpropyl]nitroxide,

N-(1-methylethyl)-1-cyclohexyl-1-(diethylphosphono)nitroxide,

N-(1-phenylbenzyl)[(1-diethylphosphono)-1-methyethyl]nitroxide,

N-phenyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide,

N-phenyl-1-diethylphosphono-1-methylethyl nitroxide,

N-(1-phenyl-2-methylpropyl)-1-diethylphosphonomethylethyl nitroxide.

Most of the intermediate compounds A(X)_(n) in which X represents achlorine atom or a bromine atom, and which are capable of generatingfree radicals, are products that are either commercially available orare obtained according to methods described in the literature.

The compounds such as those represented by formula (IVi):

are novel compounds and, as such, form part of the present invention.

In this formula, R⁵, R⁶ and R⁷, which may be identical or different,represent a linear or branched alkyl radical containing a number ofcarbon atoms ranging from 1 to 10, a phenyl radical, a benzyl radical, acycloalkyl radical containing a number of carbon atoms ranging from 3 to12, and q, r and s are integers ranging from 1 to 5.

The compounds of formula (IVi) according to the present invention wereprepared according to a method which consists in introducing an acidbromide of formula (XI):

(R⁵, R⁶ or R⁷)

with a 1,3,5-tris(α-hydroxyalkyl)cyanuric acid in an acidbromide/cyanuric acid derivative molar ratio which is substantiallyequal to 3, in heating the reaction medium at a temperature between 50°C. and 100° C., which is maintained for about 12 hours. After cooling toroom temperature, the reaction medium is taken up in a halogenatedsolvent such as CH₂Cl₂ and washed with water till neutral.

The resulting solution is dried over MgSO₄ and the solvent is removedunder reduced pressure.

The compounds obtained are identified by mass spectrometry and by ¹H and¹³NMR.

The polyalkoxyamines of formula (I) according to the present inventionmay be used for the polymerization and copolymerization of any monomercontaining a carbon-carbon double bond, which is capable of undergoingfree-radical polymerization. The polymerization or copolymerization isperformed under the usual conditions known to those skilled in the art,taking into account the monomer(s) under consideration. Thus, thepolymerization or copolymerization may be performed in bulk, insolution, in emulsion or in suspension, at temperatures ranging from 50°C. to 250° C. and preferably ranging from 70° C. to 150° C. Asnonlimiting examples of monomers which may be used according to thepresent invention, mention will be made of vinylaromatic monomers suchas styrene, substituted styrenes, dienes, acrylic monomers such as alkylor aryl acrylates and methacrylates, optionally containing fluorine, forinstance methyl acrylate, butyl acrylate or methyl methacrylate, andacrylamides such as N,N-dimethylacrylamide. The monomer may also bevinyl chloride, vinylidene difluoride or acrylonitrile.

The nitroxide—optionally corresponding to the polyalkoxyamine (I)used—may optionally be added to the polymerization medium, in anitroxide/polyalkoxyamine (I) molar ratio ranging from 0.01n % to 20n %preferably ranging from n % to 10n %.

The polyalkoxyamines (I) according to the present invention may also beused for the synthesis of “sequenced” block copolymers according to aprocedure which consists in carrying out, in a first step, the bulk,solution, suspension or emulsion polymerization of a monomer M1 or amixture of monomers containing a carbon-carbon double bond capable ofundergoing free-radical polymerization in the presence of apolyalkoxyamine (I) at a temperature ranging from 50° C. to 250° C. andpreferably ranging from 70° C. to 150° C., and then, in a second step,allowing the temperature to fall and optionally evaporating off theresidual monomer(s), and then, in a third step, in introducing themonomer M2 or a new mixture of monomers into the reaction mediumobtained above, and then resuming the polymerization by simply raisingthe temperature.

By way of example, sequenced block copolymers such aspolystyrene-polybutyl polyacrylate-polystyrene (PS-BUA-PS) may beprepared in this manner.

The examples which follow illustrate the invention.

GENERAL COMMENTS

The compounds obtained in the synthesis examples are identified by CHNmicroanalysis and by ¹H, ¹³C and ³¹P NMR.

The β-substituted nitroxide used has the formula:

and will be denoted as DEPN.

It was obtained by oxidation of diethyl2,2-dimethyl-1-(1,1-dimethylethylamino)propylphosphonate usingmeta-chloroperbenzoic acid according to a protocol described inInternational patent application WO 96/24620.

The general reaction used in Examples 1 to 9 is as follows:

The polynitrogen ligands used are:

N,N,N′,N′,N″-pentamethyldiethylenetriamine, denoted hereinbelow asPMDETA,

tris(2-pyridylmethyl)amine, denoted hereinbelow as TPA,

bipyridine, denoted hereinbelow as BIPY.

A-(X)_(n) denotes a polyfunctional core comprising n halo functions. Weused polybromo or polychloro esters, except in Example 7 in which thefollowing chloro phosphite was used:

and in Example 8 in which para-bis(1-bromoethyl)benzene was used,obtained according to a conventional method by reacting diethylbenzenewith two equivalents of N-bromosuccinimide.

In order to obtain chloro esters of Examples 3, 4 and 9, we used thefollowing standard reaction:

by directly reproducing the procedures known to those skilled in theart.

The bromo esters of Examples 1 and 2 are obtained in accordance withExample 251 of International patentapplication WO 98/40415.

The tribromo triester used in Example 5 is obtained by reacting1,3,5-tris(2-hydroxyethyl)cyanuric acid with 2-bromopropionyl bromideand is described in Example 5.

The alkoxyamines A1 and A2 are those containing sequences ofacrylate-DEPN type. Those denoted by a name of the type S1, S2, S3 or S4contain sequences of phenylethyl-DEPN type.

EXAMPLE 1 Synthesis of the Dialkoxyamine A1

The reaction is carried out in a Schlenk tube under an argon atmosphere.The 1,6-hexanediol bis(2-bromopropionate) of formula:

and the DEPN are degassed beforehand. The toluene is distilled underargon over sodium-benzophenone. 1.02 g of CuBr, 2.23 g of BIPY and 0.45g of copper powder are introduced into the 100 ml Schlenk tube. Thesystem is purged with vacuum-argon sequences and then 1.39 g of1,6-hexanediol bis(2-bromo-propionate) and 3 g of 70% DEPN dissolved in30 ml of toluene are then added. The mixture is left to react for 3.5days at room temperature with stirring. The reaction is monitored by TLC(4/1 ether/heptane eluent). At the end of the reaction, the reactionmixture is filtered through Celite. The filtrate is washed with aqueous5% copper sulfate solution and then with water. The organic phase isdried over magnesium sulfate and the solvent is then evaporated off(crude mass=2.93 g).

The product is purified by chromatography on a column of silica using a4/1 ether/heptane and then a 1/1 ether/methanol eluent. From 0.96 gused, 0.73 g of a colorless oil is recovered.

The overall yield of isolated product is 75%.

Elemental analysis: (C₃₈H₇₈N₂O₁₂P₂): calculated: C 55.9%; H 9.6%; N3.4%; found: C 55.41%; H 9.54%; N 3.58%.

¹H, ¹³C and ³¹P NMR: the product shows four asymmetric carbon atoms andone center of symmetry. The NMR signals are complex and reveal twodistinct families of isomers in 50/50 relative proportions. The ¹H, ¹³Cand ³¹P chemical shifts (solvent=CDCl₃) are given in Table 1. Thevarious atoms are referred to by an index indicated in the structuralformula A1 above. When the signals are distinct, the two families ofisomers are separated by a “;”.

TABLE 1 POSITION ¹H NMR ¹³C NMR P³¹ NMR a 1.3 (broad, 12 H) 16.5; 16.9 b3.7-4.4 (broad, 8 H) 64.9-59.7; 65.0-59.9 c 1.11-1.12 (18 H) 30.2; 29.78d 36.0; 35.67 e 3.39; 3.31 68.8; 70.1 (d, (J_(PH) ² = 32 Hz) J_(PC) ² =140 Hz) f 1.17-1.2 28.3 (broad, 18 H) g 62.0; 62.2 h 4.59 (m, J_(HH) ³ =3 Hz, 83.3; 77.6 2H) i 1.49; 1.50 19.7; 18.3 (d, J_(HH) ³ = 3 Hz, 6 H) j172.5; 174.9 k 3.7-4.7 (broad, 4 H) 62.7; 62.6 l 1.67 (4 H) 26.0 m 1.41(4 H) 28.8 P atom — — 21.59-21.61, 21.14-21.26

EXAMPLE 2 Access to the Dialkoxyamine A1 With PMDETA as Amine LigandInstead of BIPY

The procedure is the same as in Example 1. The ratios of reagents usedare: DEPN/dibromo diester=2, CuBr/dibromo diester=2, PMDETA/CuBr=2,Cu(O)/CuBr=1.

The PMDETA ligand allows the reaction time to be reduced to 3 hours.

The purification is carried out by washing the reaction mixture withwater after filtration (until a colorless aqueous phase is obtained).The product is in the form of a colorless oil.

The weight yield is quantitative.

EXAMPLE 3 Synthesis of Dialkoxyamine S1

The reaction is carried out in a Schlenk tube under an argon atmosphere.The bis β-chlorophenethyl adipate of formula:

and the DEPN are degassed beforehand. The toluene is distilled underargon over sodium-benzophenone.

3.25 g of CuBr, 7.8 g of PMDETA and 1.29 g of copper powder areintroduced into the 100 ml Schlenk tube. The system is purged withvacuum-argon sequences and 5 g of bis(β-chlorophenethyl) adipate (11.4mmol) and 7.5 g of 90% DEPN dissolved in 50 ml of toluene are thenadded. The mixture is left to react for 12 hours at room temperature.The reaction is monitored by TLC (4/1 ether/heptane eluent). At the endof the reaction, the reaction mixture is filtered through Celite. Thefiltrate is washed with water. The solvent is evaporated off and theexpected dialkoxyamine S1 is recovered in the form of a colorless oil(mixture of diastereoisomers). Quantitative yield.

Elemental analysis: C₄₈H₈₂N₂O₁₂P₂: calculated: C 61.3%; H 8.8%; N 3.0%;found: C 61.41%; H 8.62%; N 2.95%.

¹H, ¹³C, ³¹P NMR: the spectra show that by NMR there are two distinctfamilies of isomers in a 63/37 relative proportion. Table 2 summarizesthe chemical shifts of the hydrogen, carbon and phosphorus atoms indexedas on the structural formula S1. The shifts corresponding to thepredominant isomer family are underlined when they are distinguishedfrom the others.

TABLE 2 POSITION ¹H NMR ¹³C NMR ³¹P NMR a 1.2 (broad) 16.1-16.3;16.2-16.7 b 3.7 to 4.5 (m, 8H) 58.8-59.1; 61.5 c 1.2 (broad) 30.7; 30.0d / 35.3; 35.7 e 3.35; 3.40(2 H; 69.7; 69.3 J2HP = 25 Hz) (J¹CP = 139Hz) f 1.2 (broad) 27.9 g / 67.8 h 7.2 (1.0 H, H arom.) 128.6-138.9 i5.29; 5.03 79.7; 86.7 j 4.45-4.90 64.6; 65.8 k / 171.2 l 1.85-2.25 33.5;33.6 m 1.85-2.25 23.9; 23.8 P atom / / 24.2; 25.3

EXAMPLE 4 Synthesis of Dialkoxyamine S2

The reaction is carried out in a Schienk tube under an argon atmosphere.The bis(β-chlorophenethyl) succinate of formula:

and the DEPN are degassed beforehand. The toluene is distilled underargon over sodium-benzophenone.

3.25 g of CuBr, 7.8 g of PMDETA and 1.29 g of copper powder areintroduced into the 100 ml Schlenk tube. The system is purged withvacuum-argon sequences and 4.66 g of bis(β-chlorophenethyl) succinate(11.4 mmol) and 7.5 g of 90% DEPN dissolved in 50 ml of toluene are thenadded. The mixture is left to react for 12 hours at room temperaturewith stirring. The reaction is monitored by TLC (4/1 ether/heptaneeluent). At the end of the reaction, the reaction mixture is filteredthrough Celite. The filtrate is washed with water. The solvent isevaporated off and the expected product is recovered in the form of acolorless oil (mixture of diastereoisomers). Quantitative yield.

Elemental analysis: C₄₆H₇₈N₂O₁₂P₂: calculated: C 60.5%; H 8.6%; N 3.1%found: C 60.45%; H 8.58%; N 3.2%.

NMR:

The spectra show that by NMR there are two distinct families of isomersin a 60/40 relative proportion. Table 3 summarizes the chemical shiftsof the hydrogen, carbon and phosphorus atoms indexed as on thestructural formula. The shifts corresponding to the predominant familyof isomers are underlined when they are distinguished from the others.

TABLE 3 POSITION ¹H NMR ¹³C NMR ³¹P NMR a 1.2 (broad) 16.1-16.3;16.2-16.7 b 3.7 to 4.4 (m, 8 H) 58.8-61.6; 59.1-61.5 c 1.2 (broad) 30.7;30.0 d / 35.2; 35.6 e 3.34; 3.41(2H; 69.6; 69.3 J2HP = 25 Hz) (J1CP =140 Hz) f 1.21 (broad) 27.8; 28.5 g / 61.8; 61.6 h 7.2-7.3 (10 H,128.5-140.4 H arom.) i 5.28; 5.07 (2H) 79.7; 86.7 j 4.77-4.49; 4.4-4.9064.9; 66.3 (4 H) k- / 171.4 l 2.10-2.35 (4H) 28.9; 28.8 P atom / / 24.2;25.3

EXAMPLE 5 Synthesis of Trialkoxyamine A2

The starting tribromo triester has the formula

a) Synthesis of the Triester:

15 g of 1,3,5-tris(2-hydroxyethyl)cyanuric acid (57 mmol) are loadedinto a 250 ml glass reactor. 37.1 g of 2-bromopropionyl bromide (172mmol) are added dropwise and the mixture is then heated to 80° C. Thereaction mixture is left to react overnight and is then taken up indichloromethane and washed with water until neutral. The resultingsolution is dried over magnesium sulfate and evaporated. 35.6 g of avirtually colorless syrup are thus obtained (weight yield=93%). Theproduct was characterized by ¹H and ¹³C NMR.

b) Synthesis of the Trialkoxyamine:

The reaction is carried out in a Schlenk tube under an argon atmosphere.The DEPN is degassed beforehand. The toluene is distilled under argonover sodium benzophenone.

1.03 g of CuBr, 2.09 g of TPA and 0.45 g of copper powder are introducedinto the 100 ml Schlenk tube. The system is purged with vacuum-argonsequences and 1.6 g of tribromo triester synthesized in a) and 3.02 g of70% DEPN dissolved in 10 ml of toluene are then added. The mixture isleft to react for 1 hour at room temperature with stirring. The reactionmixture is filtered through Celite and the solvent is then evaporatedoff. 3.11 g of a crude product are obtained (as a colorless syrup).

The product is purified by chromatography on a column of silica, usingan ether/ethanol eluent containing 1% ethanol. From 1 g used, 0.86 g ofcolorless syrup is recovered.

The overall yield isolated product is 82%.

The product was characterized by mass spectrometry and by ¹H, ¹³C and³¹P NMR. The NMR spectra show that there are two distinct families ofisomers in a 50/50 relative proportion. The ¹H and ³¹P chemical shifts(solvent=CDCl₃) are given in Table 4. The various atoms are referred toby index on the structural formula below. When the signals are distinct,the two families of isomers are separated by a “;”.

TABLE 4 POSITION ¹H NMR ³¹P NMR a 1.25 (broad, 18 H) b 3.8-4.4 (broad,12 H) c 1.09; 1.12 (27 H) d e 3.27; 3.33 (J_(PH) ² = 25 Hz, 3H) f 1.17(27 H) g h 4.58 (m, J_(HH) ³ = 3 Hz, 3 H) i 1.49 (m, 9 H) j k 3.8-4.4(broad, 6 H) l 3.8-4.4 (broad, 6 H) P atom — 24.3-24.35-24.4;24.95-25.0-25.05

EXAMPLE 6 Use of PMDETA to Synthesize the Trialkoxyamine A2

The conditions used are: DEPN/tribromo triester=3, CuBr/tribromotriester=3, PMDETA/CuBr=2, Cu(O)/CuBr=1, solvent=toluene, T=20° C., t=7hours.

The product is purified by washing with water (5×500 ml).

The material balance is given in Table 5. The percentages oftrialkoxyamine and of mono- and dialkoxyamine were determined by ¹H and³¹P NMR. The content of residual DEPN was determined by HPLC. Thecontent of residual solvent was determined by ¹H NMR.

TABLE 5 REAGENTS 95% tribromo 55.0 g 0.079 mol triester 90% DEPN 77.2 g0.236 mol CuBr 33.9 g 0.236 mol PMDETA 81.9 g 0.472 mol Cu(O) 15.0 g0.236 mol Toluene 800 ml Crude product 95.9 g Weight yield 93%Composition (%) weight Trialkoxyamine A2 94 Di- + 3 monoalkoxyamineResidual solvent 3 Residual DEPN <0.1 (conversion = 99.9%)

EXAMPLE 7 Synthesis of the Trialkoxyamine S3

The reaction is carried out in a Schlenk tube under an argon atmosphere.The trichloro phosphite of formula:

prepared from PCl₃ and styrene oxide according to a protocol describedin U.S. Pat. No. 2,876,246, and the DEPN are degassed beforehand. Thetoluene is distilled under argon over sodium-benzophenone.

3.4 g of CuBr, 8.2 g of PMDETA and 1.5 g of copper powder are introducedinto the 100 ml Schlenk tube. The system is purged with vacuum-argonsequences and 3.9 g of the phosphite (7.9 mmol) and 7.7 g of 90% DEPNdissolved in 50 ml of toluene are then added. The mixture is left toreact for 12 hours at room temperature with stirring. The reaction ismonitored by TLC (4/1 ether/heptane eluent). At the end of the reaction,the reaction mixture is filtered through Celite. The filtrate is washedwith water. The solvent is evaporated off and the expected product isrecovered in the form of a slightly yellow oil (mixture ofdiastereomers). Yield: 3.1 g, i.e. 31%.

Elemental analysis: C₆₃H₁₁₁N₃O₁₅P₄: calculated: C 59.4%; H 8.8%; N 3.3%found: C 59.01%; H 8.59%; N 3.21%.

EXAMPLE 8 Synthesis of the Dialkoxyamine S4

The reaction is carried out in a Schlenk tube under an argon atmosphere.The para-bis(1-bromoethyl)benzene and the DEPN are degassed beforehand.The toluene is distilled under argon over sodium-benzophenone.

1.02 g of CuBr, 3 ml of PMDETA (i.e. 4 eq.) and 0.5 g of copper powderare introduced into the 100 ml Schlenk tube. The system is purged withvacuum-argon sequences and 1.03 g of para-bis(1-bromoethyl)-benzene(3.53 mmol) and 1.77 g of 88% DEPN dissolved in 20 ml of benzene arethen added. The mixture is left to react for 6 hours at room temperaturewith stirring. The reaction is monitored by TLC (4/1 ether/heptaneeluent). At the end of the reaction, the reaction mixture is filteredover Celite after addition of ether. The filtrate is washed with water.The solvent is evaporated off and an oil is recovered, which is purifiedby chromatography on a column of silica (eluent: 6/4 pentane/ethylacetate). The column does not allow separation of the variousdiastereoisomers detected by phosphorus NMR and mass spectrometry.Yield: 1.9 g, i.e. 78%.

Elemental analysis: C₃₆H₇₀N₂O₈P₂: calculated: C 59.98%; H 9.79%; N 3.88%found: C 59.96%; H 9.87%; N 3.94%.

In a conventional manner, the ³¹P NMR shows two families of peakscorresponding to two types of diastereoisomer.

³¹P NMR: first family δ=23.05-23.09-23.21; second family: 24.36-24.4.

After one night at 0° C., one of the diastereoisomers crystallizes andmay be recovered in the form of white crystals: m.p.=148° C.

The complete NMR analysis of this diastereoisomer was able to beperformed, and consists of the diastereoisomer having a phosphorus NMRchemical shift of 23.2 ppm. The ¹H and ¹³C chemical shifts are given inTable 6.

TABLE 6 POSITION ¹H NMR ¹³C NMR a 0.89 (t, J2HH = 16.4 7.08 Hz, 12 H) b3.2-3.5; 3.75-4.10 58.9 and 61.7 (broad, 8 H) (d, JPC = 7.19 and 6.1 Hz)c 1.2-1.3 (broad; 36 H 28.3 with f) d 35.4 (d, JPC = 4.9 Hz) e 3.39(J2PH = 26 Hz, 70.1 (d, JPC = 139 2 H) Hz) f see c 30.7 (d, JPC = 5.9Hz) g 61.3 h 5.22 (q, J3HH = 6.5 78.2 Hz 2 H) i 1.51 (d, J3HH = 6.5 21.3Hz 6 H) j 142.5 k and l 7.44 (s, 4 H with 1) 127.4

EXAMPLE 9 Synthesis of the Dialkoxyamine AS1

The reaction is carried out in a Schlenk tube under an argon atmosphere.The following dichloro ester:

and the DEPN are degassed beforehand. The toluene is distilled underargon over sodium-benzophenone.

2.86 g of CuBr, 6.9 g of PMDETA and 1.2 g of copper powder areintroduced into the 100 ml Schlenk tube. The system is purged withvacuum-argon sequences and 2.46 g of the dichloro ester (10 mmol) and6.44 g of 90% DEPN dissolved in 40 ml of toluene are then added. Themixture is left to react for 12 hours at room temperature with stirring.The reaction is monitored by TLC (4/1 ether/heptane eluent). At the endof the reaction, the reaction mixture is filtered through Celite. Thefiltrate is washed with water. The solvent is evaporated off and theexpected product is recovered in the form of a slightly yellow oil(mixture of diastereoisomers). Yield: 6.9 g, i.e. 90%.

Analysis

Elemental analysis: C₃₇H₇₀N₂O₁₀P₂: calculated: C 58.1%; H 9.2%; N 3.7%found: C 58.15%; H 9.35%; N 3.6%.

EXAMPLES OF CONTROLLED FREE-RADICAL POLYMERIZATION USING THEPOLYALKOXYAMINES OF THE PRESENT INVENTION

The polymerizations were carried out under the following conditions:

Styrene or butyl acrylate are distilled and stored under an inertatmosphere at 5° C.

−1° The polyalkoxyamine and a monomer or a mixture of monomers areintroduced into a Schlenk tube which has been predried under vacuum. Themixture is degassed by sparging with nitrogen for 20 minutes, and isthen brought to the polymerization temperature. Samples are withdrawnusing a syringe purged with nitrogen.

Analyses:

The number-average masses (Mn) and the polydispersity indices (Ip) weremeasured by steric exclusion chromatography (SEC). The chromatogramswere recorded using a Spectra Physics machine fitted with an SP8810pump, a Shodex RE-61RI differential refractometer, two PIgel mixed Dcolumns (eluent: THF, 30° C.). The calibrations were carried out withstandard polystyrene samples. The polystyrenes obtained are analyzeddirectly relative to these references, whereas the polybutyl acrylatesare measured according to the universal calibration method.

The conversion was measured both by the SEC and ¹H Nuclear MagneticResonance spectra on a Bruker 200 MHz spectrometer.

The examples which follow are defined by the following parameters: massof monomer, mass of alkoxyamine, target theoretical molar mass (Mn(th)),temperature.

The results of each experiment are characterized by the reaction time,the conversion, the Mn(ex) of the polymer and the polydispersity indexIp. In certain cases, the curves indicating the conversion as a functionof time and the Mn as a function of the conversion are reported.

A) BULK POLYMERIZATION OF STYRENE EXAMPLE 1A Polymerization Compound A1

Data: mass of dialkoxyamine A1: 1 g; mass of styrene: 48 g Mn(Th) = 40000 g/mol; T = 123° C.

The results are given in Table 7.

TABLE 7 Con- Time version Mn(Th) Mn(ex) MnTh/ (min) In(M°/M) (%) (g/mol)(g/mol) Mnex 30 0.4 33 13 200 12 000 1.1 60 0.6 45 18 000 15 000 1.2 900.82 56 22 400 18 500 1.21 120 1.12 67 26 800 21 500 1.25 150 1.43 76 30400 24 500 1.24 180 1.6 80 32 000 26 000 1.23

The polydispersity index Ip at the end of polymerization is 1.3.

The curve Mn as a function of the conversion—FIG. 1—shows that thepolymerization with the dialkoxyamine A1 is well controlled. In thisFIG. 1:

—O—O— represents MnTh

—X— represents Mn(ex).

EXAMPLE 2A

Data: Polymerization with compound A2: mass of trialkoxyamine A2: 1 g;mass of styrene: 45 g Mn(Th) = 60 000 g/mol; T = 123° C.

The results are given in Table 8.

TABLE 8 Con- Time version Mn(Th) Mn(ex) MnTh/ (min) In(M°/M) (%) (g/mol)(g/mol) Mnex 30 0.35 30 18 000 20 000 0.9 60 0.6 45 27 000 30 000 0.9 900.8 55 33 000 32 500 1.02 120 1.05 65 39 000 40 000 0.98 150 1.22 70 42000 44 000 0.95 180 1.55 79 47 400 59 000 0.8

The polydispersity index Ip at the end of polymerization is: 1.4. Thecurve Mn as a function of the conversion—FIG. 2—clearly shows that thepolymerization with the trialkoxyamine A2 is well controlled. In thisFIG. 2:

—O— represents MnTh

▪ represents Mn(ex).

EXAMPLE 3a

Data: Polymerization with the compound S4: mass of dialkoxyamine S4: 1g; mass of styrene: 55 g Mn(Th) = 40 000 g/mol; T = 123° C.

The results are given in Table 9.

TABLE 9 Con- Time version Mn(Th) Mn(ex) MnTh/ (min) In(M°/M) (%) (g/mol)(g/mol) Mnex 0 0 0 0 0 0 30 0.32 27 10 800 10 500 1.03 60 0.52 41 16 40014 500 1.13 90 0.7 50 20 000 18 000 1.11 120 0.84 57 22 800 23 000 0.99150 1.09 66 26 400 24 500 1.08 180 1.4 75 30 000 25 500 1.18 210 1.65 8132 400 28 500 1.14

The polydispersity index at the end of polymerization is: 1.27. Thecurve Mn as a function of the conversion—FIG. 3—clearly shows that thepolymerization with the trialkoxyamine S4 is well controlled. In thisFIG. 3:

—O— represents MnTh,

▪ represents Mn(ex).

EXAMPLE 4A

Data: Polymerization with the compound S1: mass of dialkoxyamine S1: 1g; mass of styrene: 40 g Mn(Th) = 40 000 g/mol; T = 123° C. Results:After 3 hours, the sample withdrawn indicates a conversion of 83% for anMn of 29 000 g/mol, i.e. Mn(th)/Mn(ex) = 1.14. Ip = 1.21.

EXAMPLE 5A

Data: Polymerization with the compound S3 mass of trialkoxyamine: 1 g;mass of styrene: 46 g Mn(Th) = 60 000 g/mol; T = 123° C. Results: After3 hours, the sample withdrawn indicates a conversion of 83% for an Mn of50 500 g/mol, i.e. Mn(th)/Mn(ex) = 0.89. Ip = 1.36. B) BULKPOLYMERIZATION OF BUTYL ACRYLATE (BUA)

EXAMPLE 1B

Data: Polymerization with compound S4 mass of dialkoxyamine S4: 1 g;mass of BUA: 55 g Mn(Th) = 40 000 g/mol; T = 123° C.

The results are given in Table 10.

TABLE 10 Con- Time version Mn(Th) Mn(ex) MnTh/ (min) In(M°/M) (%)(g/mol) (g/mol) Mnex 0 0 0 0 0 0 30 0.8 55 22 000 16 000 1.38 60 1.1 6726 800 20 000 1.34 90 2.3 90 36 000 28 500 1.26

The polydispersity index Ip at the end of polymerization is: 1.7.

C) IMPROVEMENT OF THE POLYMERIZATION OF BUTYL ACRYLATE (BUA) BY ADDINGCOMONOMER TO THE INITIAL MASS

In the following examples for obtaining a better control of thepolymerization of butyl acrylate, we added 5% of styrene to the acrylateand we started the polymerization of this mixture.

EXAMPLE 1C

Data: Polymerization with the compound A1: mass of dialkoxyamine A1: 1g; mass of butyl acrylate/styrene (95/5) mixture: 48 g Mn(Th) = 40 000g/mol; T = 123° C.

The results are given in Table 11.

TABLE 11 Time Con- Mn Th Mn(ex) MnTh/ (min) In(M°/M) version(%) (g/mol)(g/mol) Mn(ex) 0 0 0 0 0 0 30 0.45 36 14 400 12 000 1.2 60 0.8 55 22 00015 000 1.47 90 1.35 74 29 600 18 500 1.6 120 1.71 82 32 800 21 500 1.53

The polydispersity index Ip at the end of polymerization is: 1.4. Thecurve Mn as a function of the conversion—FIG. 4—clearly shows that thepolymerization with the alkoxyamine A1 is well controlled. In this FIG.4:

—O— represents MnTh

▪ represents Mn(ex).

EXAMPLE 2C

Data: Polymerization with the compound A2: mass of trialkoxyamine A2: 1g; mass of butyl acrylate/styrene (95/5) mixture: 45 g; Mn(Th) = 60 000g/mol; T = 123° C.

The results are given in Table 12.

TABLE 12 Time Con- Mn Th Mn(ex) MnTh/ (min) In(M°/M) version(%) (g/mol)(g/mol) Mn(ex) 0 0 0 0 0 0 30 0.55 42 25 200 23 000 1.1 60 1.1 67 40 20032 000 1.26 90 1.6 80 48 000 40 000 1.2

The polydispersity index Ip at the end of polymerization is: 1.4. Thecurve Mn as a function of the conversion—FIG. 5—clearly indicates thatpolymerization with the trialkoxyamine A2 is well controlled. In thisFIG. 5:

—O— represents MnTh

▪ represents Mn exp.

D) PRODUCTION OF A BLOCK COPOLYMER PS-PABU-PS EXAMPLE 1D PolymerizationWith the Compound A1

1st Block: polymerization according to Example 1c.

Data: mass of dialkoxyamine A1: 1 g; mass of butyl acrylate/styrene(95/5) mixture: 97 g Mn(Th) = 81 200 g/mol; T = 123° C. Results: After 2hours, the temperature is allowed to fall. A 72% conversion (MnTh = 58500) is obtained for an Mn of 55 300 (Mn(th)/Mn(exp) = 1.05) and apolydispersity index Ip = 1.3.

The residual monomer is evaporated off under reduced pressure.

2nd Block:

The polymer obtained is diluted in styrene (260 g). The temperature ofthe reactor is raised to 123° C. The polymerization is then reviewed andis stopped after 30 min at 10% conversion such that the polystyreneblocks at the two ends of each chain have a length of 6 500 g/mol, i.e.an Mn(th)=68 400 g/mol for the polymer.

Results:

Mn=73 900 g/mol (Mn(th)/Mn(exp)=0.93), Ip=1.7.

What is claimed is:
 1. A compound of formula (I):

in which: A represents a divalent or polyvalent structure; R_(L)represents a monovalent radical with a molar mass of greater than 15 andn≧2.
 2. A compound according to claim 1, wherein A is chosen from thefollowing formulas II-IX:

in which R¹ and R², which may be identical or different, are each alinear or branched alkyl radical containing 1 to 10 carbon atoms, aphenyl or thienyl radical which is optionally substituted with a halogenatom, a linear or branched alkyl radical containing 1 to 4 carbon atoms,nitro, alkoxy, aryloxy, carbonyl or carboxyl, a benzyl radical, or acycloalkyl radical containing 3 to 12 carbon atoms, or a radicalcomprising one or more unsaturations; B is a linear or branched alkyleneradical containing 1 to 20 carbon atoms; and m is an integer rangingfrom 1 to 10;

in which R³ and R⁴, which may be identical or different, are each aryl,pyridyl, furyl or thienyl which in each case is optionally substitutedwith a halogen atom, a linear or branched alkyl radical containing 1 to4 carbon atoms, nitro, alkoxy, aryloxy, carbonyl or carboxyl; D is alinear or branched alkylene radical containing 1 to 6 carbon atoms, aphenylene radical or a cycloalkylene radical; and p is 0 to 10;

in which R⁵, R⁶ and R⁷, which may be identical or different, are each alinear or branched alkyl radical containing 1 to 10 carbon atoms, aphenyl or thienyl radical which is optionally substituted with a halogenatom, a linear or branched alkyl radical containing 1 to 4 carbon atoms,nitro, alkoxy, aryloxy, carbonyl or carboxyl, a benzyl radical, or acycloalkyl radical containing 3 to 12, or a radical comprising one ormore unsaturations; and q, r and s are each integers ranging from 1 to5;

in which R⁸ is aryl, pyridyl, furyl or thienyl which in each case isoptionally substituted with a halogen atom, a linear or branched alkylradical containing 1 to 4 carbon atoms, nitro, alkoxy, aryloxy, carbonylor carboxyl, t is an integer ranging from 1 to 4, and u is ≧2 and ≦6;

in which R⁹ is aryl, pyridyl, furyl or thienyl which in each case isoptionally substituted with a halogen atom, a linear or branched alkylradical containing 1 to 4 carbon atoms, nitro, alkoxy, aryloxy, carbonylor carboxyl, and v is ≧2 and ≦6;

in which R¹⁰, R¹¹ and R¹², which may be identical or different, are eachphenyl optionally substituted with a halogen atom, or a linear orbranched alkyl radical containing 1 to 10 carbon atoms; W is an oxygen,sulfur or selenium atom, and w is equal to zero or 1;

in which R¹³ is a linear or branched alkyl radical containing 1 to 10carbon atoms, a phenyl or thienyl radical which is optionallysubstituted with a halogen atom, a linear or branched alkyl radicalcontaining 1 to 4 carbon atoms, nitro, alkoxy, aryloxy, carbonyl orcarboxyl, a benzyl radical, or a cycloalkyl radical containing 3 to 12,or a radical comprising one or more unsaturations; and R¹⁴ is aryl,pyridyl, furyl or thienyl which in each case is optionally substitutedwith a halogen atom, a linear or branched alkyl radical containing 1 to4 carbon atoms nitro, alkoxy, aryloxy, carbonyl or carboxyl; and

in which R¹⁵ and R¹⁶, which may be identical or different, are each ahydrogen atom, a linear or branched alkyl radical containing 1 to 10carbon atoms, or an aryl radical, optionally substituted with a halogenatom or a hetero atom.
 3. A compound according to claim 1, wherein R_(L)has a molar mass greater than
 30. 4. A compound according to claim 3,wherein R_(L) has a molar mass ranging from 40 to
 450. 5. A compoundaccording to claim 1, wherein the remaining valencies of the carbon atombearing R_(L) and of the nitrogen atom of formula (I) are linked tomonovalent radicals or are linked together via a divalent radical so asto form a ring.
 6. A compound according to claim 1, wherein theremaining monovalent radicals linked to the carbon atom bearing R_(L)which may be identical of different, are a hydrogen atom, a linear orbranched alkyl radical containing 1 to 12 carbon atoms, a phenyl radicalor an aralkyl radical containing 1 to 10 carbon atoms.
 7. A compoundaccording to claim 1, wherein the remaining valency of the nitrogen islinked to a monovalent group —C(CH₃)₂Z wherein Z is —CO₂alkyl, —CO₂H,—CH₃, —CN, —CH₂OH or —CH₂OSi(CH₃)₃.
 8. A compound according to claim 1,wherein R_(L) comprises a phosphoryl group.
 9. A compound according toclaim 8, wherein R_(L) is of the formula:

in which R¹⁷ and R¹⁸, which may be identical or different, are each ahalogen, alkyl, cycloalkyl, alkoxy, aryloxy, aryl, aralkyloxy,perfluoroalkyl or aralkyl.
 10. A compound according to claim 9, whereinR¹⁷ and R¹⁸ each contain 1 to 20 carbon atoms.
 11. A compound accordingto claim 1, wherein in formula (I) n is 2 and at least one of theremaining valencies of the carbon atom bearing R_(L) is linked to ahydrogen atom.
 12. A polyalkoxyamine of formula:


13. A polyalkoxyamine of formula:


14. A polyalkoxyamine of formula:


15. A polyalkoxyamine of formula:


16. A polyalkoxyamine of formula:


17. A polyalkoxyamine of formula:


18. A polyalkoxyamine of formula:


19. A compound of formula:

in which R⁶, R⁷ and R⁸, which may be identical or different, are each alinear or branched alkyl radical containing 1 to 10 carbon atoms, aphenyl radical, a benzyl radical or a cycloalkyl radical containing 3 to12 carbon atoms, and q, r and s are each integers ranging from 1 to 5.20. A process comprising polymerizing at least one monomer containing acarbon-carbon double bond which is capable of undergoing bulk, solution,emulsion or suspension free radical polymerization, at a temperature of50° C. to 250° C., wherein polymerization is performed in the presenceof a compound according to claim 1, as a polymerization initiator.
 21. Aprocess as claimed in claim 20, wherein the polymerized monomer(s) is(are) vinylaromatic monomers optionally fluorinated acrylic monomersacrylamides or acrylonitrile.
 22. A process as claimed in claim 20,wherein the polymerization is carried out in bulk.
 23. A process asclaimed in claim 20, wherein the polymerization is carried out insolution.
 24. A process as claimed in claim 20, wherein thepolymerization is carried out in emulsion.
 25. A process as claimed inclaim 20, wherein the polymerization is carried out in suspension.
 26. Aprocess as claimed in claim 20, wherein a further nitroxide, which doesor does not correspond to a nitroxide from which the compound of formula(I) is obtained is also used.
 27. A process as claimed in claim 26,wherein the nitroxide/polyalkoxyamine (I) molar ratio ranges from 0.01n% to 20n %.
 28. A process as claimed in claim 20, wherein a mixture ofmonomers in variable proportions is polymerized.
 29. A process asclaimed in claim 28, wherein the mixture of monomers comprises at leastone alkyl acrylate in a weight proportion of not more that 99.5%.
 30. Aprocess as claimed in claim 29, wherein the mixture of monomers is amixture of alkyl acrylate and of a styrene olefin with a weight contentof alkyl acrylate of between 88% and 97%.
 31. A process as claimed inclaim 29, wherein the alkyl acrylate is butyl acrylate.
 32. A process asclaimed in claim 20, wherein sequenced block copolymers are synthesized.33. A process as claimed in claim 32, wherein the sequenced blockcopolymers are obtained according to a process which consists incarrying out, in a first step, polymerizing a monomer M1 or of a mixtureof monomers containing a carbon-carbon double bond which is capable ofundergoing a free-radical polymerization in the presence of a compoundof formula (I) at a temperature ranging from 50° C. to 250° C.; andthen, in a second step, allowing the temperature to fall, and optionallyevaporating off unreacted residual monomer(s); and then, in a thirdstep, introducing into the reaction medium a second monomer M2 or a newmixture of monomers; and then resuming polymerization by raising thetemperature.
 34. A process as claimed in claim 33, wherein M1 anoptionally fluorinated alkyl acrylate and M2 is a styrene olefin.
 35. Aprocess as claimed in claim 33, wherein M1 is butyl acrylate and M2 isstyrene.
 36. A polymer or copolymer obtained as claimed in claim
 20. 37.A process according to claim 20, wherein said monomer is a vinylaromaticmonomer, a diene monomer, an acrylic monomer, an acrylamide monomer,vinyl chloride, vinylidene fluoride, or acrylonitrile.
 38. A compoundaccording to claim 1, wherein the remaining monovalent radicals linkedto the carbon atom bearing R_(L), which may be identical of different,are each independently hydrogen, linear or branched alkyl containing 1to 12 carbon atoms, phenyl, or aralkyl containing 1 to 10 carbon atoms;the remaining valency of the nitrogen is linked to monovalent group—C(CH₃)₂Z wherein Z is —CO₂alkyl, —CO₂H, —CH₃, —CN, —CH₂OH or—CH₂OSi(CH₃)₃; and A is chosen from the structures below:

wherein R¹ and R², which may be identical or different, each representlinear or branched alkyl containing 1 to 10 carbon atoms, phenyl orthienyl which is optionally substituted by F, Cl, Br, linear or branchedalkyl containing 1 to 4 carbon atoms, nitro, alkoxy, aryloxy, carbonylor carboxyl, benzyl, or cycloalkyl containing 3 to 12 carbon atoms, andB is linear or branched alkylene containing 1 to 20 carbon atoms, and mis an integer ranging from 1 to 10;

wherein R³ and R⁴, which may be identical or different, are each aryl,pyridyl, furyl or thienyl which in each case is optionally substitutedby F, Cl or Br, linear or branched alkyl containing 1 to 4 carbon atoms,nitro, alkoxy, aryloxy, carbonyl or carboxyl, D is linear or branchedalkylene containing 1 to 6 carbon atoms, phenylene or cycloalkylene, andp is 0 to 10;

wherein R⁵, R⁶ and R⁷, which may be identical or different, eachrepresent linear or branched alkyl containing 1 to 10 carbon atoms,phenyl or thienyl which is optionally substituted by F, Cl, Br, linearor branched alkyl containing 1 to 4 carbon atoms, nitro, alkoxy,aryloxy, carbonyl or carboxyl, benzyl, or cycloalkyl containing 3 to 12carbon atoms, and q, r and s are each integers ranging from 1 to 5;

wherein R⁸ is aryl, pyridyl, furyl or thienyl which in each case isoptionally substituted by F, Cl or Br, linear or branched alkylcontaining 1 to 4 carbon atoms, nitro, alkoxy, aryloxy, carbonyl orcarboxyl, t is an integer ranging from 1 to 4, and u is ≧2 and ≦6;

wherein R⁹ is aryl, pyridyl, furyl or thienyl which in each case isoptionally substituted by F, Cl or Br, linear or branched alkylcontaining 1 to 4 carbon atoms, nitro, alkoxy, aryloxy, carbonyl orcarboxyl, and v is ≧2 and ≦6;

wherein R¹⁰, R¹¹ and R¹², which may be identical or different, are eachphenyl which is optionally substituted by Cl or Br, or linear orbranched alkyl containing 1 to 10 carbon atoms ranging from; W isoxygen, sulfur or selenium, and w is equal to zero or 1;

wherein R¹³ is linear or branched alkyl containing 1 to 10 carbon atoms,phenyl or thienyl which is optionally substituted by F, Cl, Br, linearor branched alkyl containing 1 to 4 carbon atoms, nitro, alkoxy,aryloxy, carbonyl or carboxyl, benzyl, or cycloalkyl containing 3 to 12carbon atoms, and R¹⁴ is aryl, pyridyl, furyl or thienyl which in eachcase is optionally substituted by F, Cl or Br, linear or branched alkylcontaining 1 to 4 carbon atoms, nitro, alkoxy, aryloxy, carbonyl orcarboxyl; and

wherein R¹⁵ and R¹⁶, which may be identical or different, are eachhydrogen, linear or branched alkyl containing 1 to 10 carbon atoms, oraryl optionally substituted with a halogen atom.
 39. A compoundaccording to claim 1, wherein R_(L) is of formula (X)

wherein R¹⁷ and R¹⁸, which may be identical or different, are each ahalogen, or alkyl, cycloalkyl, alkoxy, aryloxy, aryl, aralkyloxy,perfluoroalkyl or aralkyl, in each case having up to 20 carbon atoms.40. A process comprising polymerizing at least one monomer containing acarbon-carbon double bond which is capable of undergoing bulk, solution,emulsion or suspension free radical polymerization, at a temperature of50° C. to 250° C., wherein polymerization is performed in the presenceof a compound according to claim 38, as a polymerization initiator. 41.A process comprising polymerizing at least one monomer containing acarbon-carbon double bond which is capable of undergoing bulk, solution,emulsion or suspension free radical polymerization, at a temperature of50° C. to 250° C., wherein polymerization is performed in the presenceof a compound according to claim 40, as a polymerization initiator. 42.A process as claimed in claim 40, wherein the polymerized monomer(s) is(are) vinylaromatic monomers or optionally fluorinated acrylic monomers.43. A process as claimed in claim 41, wherein the polymerized monomer(s)is (are) vinylaromatic monomers or optionally fluorinated acrylicmonomers.
 44. A process as claimed in claim 21, wherein the polymerizedmonomer(s) is (are) styrene, optionally fluorinated alkyl or arylacrylate, optionally fluorinated alkyl or aryl methacrylate, anacrylamide or acrylonitrile.
 45. A process according to claim 33,wherein said free-radical polymerization is performed at a temperatureof 70° C. to 150° C.
 46. A compound as claimed in claim 9, wherein R⁶,R⁷, and R⁸ are each CH₃— and q, r, and s are each 2.